In the heady days of Barack Obama’s campaign for the White House in 2008, the soon-to-be president made a speech at the Cuban American National Foundation that was to become a benchmark for his relations with a hemisphere.

“It’s time for a new alliance of the Americas,” the candidate declared. “It’s time to turn the page on the arrogance of Washington and the anti-Americanism across the region that stands in the way of progress.”

He went on to promise that he would engage Cuba, help to end the conflict in Colombia, boost democracy and development in Haiti, crack down on drug cartels in Mexico and strengthen trade and aid to Latin America as a whole.

After the stagnation of the Bush era, this sounded like a bold step forward, particularly given the regional mood at the time. Venezuela’s Hugo Chávez was in his Washington-bashing pomp. Leftwing administrations dominated the continent. China’s influence was on the rise.

Even after Obama entered the White House, many doubted he would fare any better than his predecessors in winning the hearts and minds of his regional neighbours. The nerdy northern president looked like a soft touch compared with the caudillo hard-men of the south.

Amid all the euphoria over the thaw, it is sobering to look back at the other promises Obama made to Cuba in 2008

Fast forward eight years, however, and it is undoubtedly Obama’s vision that is in the ascendant. On Sunday, he will be in his pomp as the first sitting US president in 88 years to visit Havana, a move that looks likely to be remembered among the greatest legacies of his presidency. Meanwhile, the regional leaders who once isolated him are falling like flies. Declining commodity prices, election defeats and corruption investigations are reversing the “pink tide” of the Latin left that was once a source of hope for socialists around the world.

The past week has seen massive anti-government demonstrations in Brazil and a heightened legal challenge against former Workers party president Luiz Inácio Lula da Silva. Last month, Bolivia’s formerly unbeatable president Evo Morales lost his first election – a referendum that would have changed the constitution so he could remain in power until the middle of the next decade.

His regional swagger was not always so confident. In the early days of his presidency, it looked as though his pledge of better neighborhood relations was just froth and talk, designed only to win over the sizeable Hispanic vote. Like many a president before him, Obama devoted his foreign policy attention to the Middle East and Russia. Latin America appeared an afterthought. Disappointed regional leaders turned against him. At the Summit of the Americas in Cartagena, Colombia, in April 2012, the US looked more isolated than ever.

The main cause of friction was US policy towards Cuba. Washington’s cold war embargo and its work to block Havana from neighbors was seen as a part of the arrogance and interference that had characterized US policy for decades. It left every other plan snarled in resentment.

But by reaching out with a surprise pope-brokered agreement with Raúl Castro on 17 December 2014, Obama appears to have cut this Gordian knot. At last year’s Summit of the Americas in Panama, he shook hands and talked to Castro, held a 10-minute dialogue with Chávez’ successor, and won plaudits (as well as the usual brickbats) from other leaders.

A billboard in Cuba: ‘Socialism or death’. Photograph: Enrique de la Osa/Reuters

Speaking at a panel in Washington this week, Mike Hammer, the US ambassador to Chile, said that normalized relations with Cuba go a long way to “removing what we all know was a tension point in US relations with the hemisphere”.

“It’s good for folks back here in Washington to grasp that,” he said, adding: as ambassador of Chile I can see, even among regular people that come up and say, ‘Well, it was about time,’ and ‘It was the right thing to do,’ really it’s quite significant.”

More acclaim is likely to follow in the next week, but amid all the euphoria over the thaw, it is sobering to look back at the other promises Obama made to Cuba and the region in 2008. The overall score card is good, but by no means perfect.

Running for president in the critical state of Florida, he told Miami’s powerful Cuban community that he would only engage the Castro government to stand up for freedom. He said he would push for the release of political prisoners – a goal that has been largely but not completely achieved – but also vowed to promote freedom of the press, freedom of assembly and political reforms necessary for free elections. None of these latter three is close to success. This next week may move the needle, but not by much.

Another 2008 promise, peace in Colombia, may do far more. Negotiations in Havana are expected to reach agreement very soon on an end to the world’s oldest conflict, the almost 70-year war between the government in Bogota and leftist guerrillas. The US, Cuba and Venezuela are among the key players backing a deal.